Compounds and combinations thereof for treating neurological and psychiatric conditions

ABSTRACT

This disclosure relates to administration of a combination of: 1) about 100-110 mg, about 104-106 mg, or about 105 mg of bupropion hydrochloride, or a molar equivalent amount of a free base form or another salt form of bupropion; and 2) about 40-50 mg, about 44-46 mg, or about 45 mg of dextromethorphan hydrobromide, or a molar equivalent amount of a free base form or another salt form of dextromethorphan in certain patient populations, such as patients having moderate renal impairment, patients receiving a concomitant strong CYP2D6 inhibitor, patients who are known CYP2D6 poor metabolizers, those in need of an NMDA antagonist that does not cause dissociation, and those at risk of QT prolongation.

SUMMARY

This disclosure relates to administration of a combination of: 1) about 100-110 mg, about 104-106 mg, or about 105 mg of bupropion hydrochloride, or a molar equivalent amount of a free base form or another salt form of dextromethorphan; and 2) about 40-50 mg, about 44-46 mg, or about 45 mg of dextromethorphan hydrobromide, or a molar equivalent amount of a free base form or another salt form of dextromethorphan in certain patient populations.

Some embodiments include a method of treating major depressive disorder in a patient having moderate renal impairment, comprising administering a daily dose of: (i) about 105 mg of bupropion hydrochloride and (ii) about 45 mg of dextromethorphan hydrobromide to a human patient who has moderate renal impairment and is experiencing major depressive disorder.

Some embodiments include a method of treating a patient having a nervous system condition by administering a combination of dextromethorphan and bupropion, the method comprising:

-   -   orally administering to the patient, once a day, a dosage form         comprising: 105 mg or less of bupropion hydrochloride, or a         molar equivalent amount of the free base or another salt form of         bupropion, and 45 mg or less of dextromethorphan hydrobromide,         or a molar equivalent amount of the free base or another salt         form of dextromethorphan, wherein the molar ratio of the         bupropion to the dextromethorphan in the dosage form is about         the ratio of the molar amount bupropion in 105 mg of bupropion         hydrochloride to the molar amount of dextromethorphan in 45 mg         of dextromethorphan hydrobromide;     -   wherein the patient is selected for: 1) having the nervous         system condition and 2) having moderate renal impairment,         wherein the patient is determined to have moderate renal         impairment by an assay on a biological sample from the patient;         and     -   wherein a risk of somnolence or dizziness for the patient who         has moderate renal impairment is lower following orally         administering the dosage form containing the combination once a         day to the patient than it would be if a combination of 105 mg         of bupropion hydrochloride and 45 mg of dextromethorphan         hydrobromide were administered twice a day to the patient for         the same number of days.

Some embodiments include a method of treating a patient with a combination of dextromethorphan and bupropion, wherein the patient is experiencing a nervous system condition, the method comprising the steps of:

-   -   determining whether the patient has moderate renal impairment         by:         -   obtaining or having obtained a biological sample from the             patient; and         -   performing or having performed an assay on the biological             sample to determine if the patient has moderate renal             impairment; and     -   if the patient has moderate renal impairment, then orally         administering once a day to the patient, a dosage form         containing a combination of 105 mg or less of bupropion         hydrochloride, or a molar equivalent amount of the free base or         another salt form of bupropion, and 45 mg or less of         dextromethorphan hydrobromide, or a molar equivalent amount of         the free base or another salt form of dextromethorphan, wherein         the molar ratio of the bupropion to the dextromethorphan is         about the ratio of the molar amount of bupropion in 105 mg of         bupropion hydrochloride to the molar amount of dextromethorphan         in 45 mg of dextromethorphan hydrobromide;     -   if the patient does not have renal impairment, then orally         administering twice a day to the patient, a dosage form         containing a combination of 105 mg of bupropion hydrochloride,         or a molar equivalent amount of the free base or another salt         form of bupropion, and 45 mg of dextromethorphan hydrobromide,         or a molar equivalent amount of the free base or another salt         form of dextromethorphan;     -   wherein a risk of somnolence or dizziness for a patient who has         moderate renal impairment is lower following orally         administering the dosage form containing the combination once a         day to the patient than it would be if a combination of 105 mg         of bupropion hydrochloride and 45 mg of dextromethorphan         hydrobromide were administered twice a day to the patient for         the same number of days.

Some embodiments include a method of treating a patient who is experiencing a nervous system condition, the method comprising the steps of:

-   -   a) determining whether the patient is at risk of an adverse         event associated with overexposure to dextromethorphan by:         -   obtaining or having obtained a biological sample from the             patient; and performing or having performed an assay on the             biological sample to determine if the patient has moderate             renal impairment, wherein a result that the patient has             moderate renal impairment indicates that the patient is at             risk of an adverse event associated with overexposure to             dextromethorphan; and     -   b) if the patient is at risk of an adverse event associated with         overexposure to dextromethorphan, then orally administering once         a day to the patient, a dosage form containing a combination of         105 mg or less of bupropion hydrochloride, or a molar equivalent         amount of the free base or another salt form of bupropion, and         45 mg or less of dextromethorphan hydrobromide, or a molar         equivalent amount of the free base or another salt form of         dextromethorphan, wherein the molar ratio of the bupropion to         the dextromethorphan is about the ratio the molar amount of         bupropion in 105 mg of bupropion hydrochloride to the molar         amount of dextromethorphan in 45 mg of dextromethorphan         hydrobromide; and     -   c) if the patient is not at risk of an adverse event associated         with overexposure to dextromethorphan, then orally administering         twice a day to the patient, a dosage form containing a         combination of 105 mg of bupropion hydrochloride, or a molar         equivalent amount of the free base or another salt form of         bupropion, and 45 mg of dextromethorphan hydrobromide, or a         molar equivalent amount of the free base or another salt form of         dextromethorphan.

Some embodiments include a method of treating a nervous system condition with a combination of dextromethorphan and bupropion, comprising:

-   -   orally administering to a patient, once a day, a dosage form         containing a combination of 105 mg or less of bupropion         hydrochloride, or a molar equivalent amount of the free base or         another salt form of bupropion, and 45 mg or less of         dextromethorphan hydrobromide, or a molar equivalent amount of         the free base or another salt form of dextromethorphan, wherein         the molar ratio of bupropion to dextromethorphan in the dosage         form is about the ratio of the molar amount of bupropion in 105         mg of bupropion hydrochloride to the molar amount of         dextromethorphan in 45 mg of dextromethorphan hydrobromide; and     -   wherein the patient is selected for: 1) having the nervous         system condition and 2) having moderate renal impairment,         wherein the patient is determined to have moderate renal         impairment by an assay on a biological sample from the patient;         and     -   wherein the patient has a reduced risk of an adverse event as         compared with the risk of the adverse event that the patient         would have if the dosage form were administered twice daily to         the patient.

Some embodiments include a method of treating a patient with a combination of dextromethorphan and bupropion, wherein the patient is experiencing a nervous system condition, the method comprising the steps of:

-   -   determining whether the patient has moderate renal impairment         by:         -   obtaining or having obtained a biological sample from the             patient; and         -   performing or having performed an assay on the biological             sample to determine if the patient has moderate renal             impairment; and     -   if the patient has moderate renal impairment, then orally         administering once a day to the patient, a dosage form         containing a combination of 105 mg or less of bupropion         hydrochloride, or a molar equivalent amount of the free base or         another salt form of bupropion, and 45 mg or less of         dextromethorphan hydrobromide, or a molar equivalent amount of         the free base or another salt form of dextromethorphan, wherein         the molar ratio of bupropion to dextromethorphan in the dosage         form is about the ratio of the molar amount of bupropion in 105         mg of bupropion hydrochloride to the molar amount of         dextromethorphan in 45 mg of dextromethorphan hydrobromide; and     -   if the patient does not have renal impairment, then orally         administering twice a day to the patient, a dosage form         containing a combination of 105 mg of bupropion hydrochloride,         or a molar equivalent amount of the free base or another salt         form of bupropion, and 45 mg of dextromethorphan hydrobromide,         or a molar equivalent amount of the free base or another salt         form of dextromethorphan.

Some embodiments include a method of treating a patient having a nervous system condition by administering a combination of dextromethorphan and bupropion, the method comprising:

-   -   orally administering to the patient, once a day, a dosage form         comprising: 105 mg or less of bupropion hydrochloride, or a         molar equivalent amount of the free base or another salt form of         bupropion, and 45 mg or less of dextromethorphan hydrobromide,         or a molar equivalent amount of the free base or another salt         form of dextromethorphan, wherein the molar ratio of the         bupropion to the dextromethorphan in the dosage form is about         the ratio of the molar amount bupropion in 105 mg of bupropion         hydrochloride to the molar amount of dextromethorphan in 45 mg         of dextromethorphan hydrobromide;     -   wherein the patient is selected for: 1) having the nervous         system condition and 2) having moderate renal impairment,         wherein the patient is determined to have moderate renal         impairment by an assay on a biological sample from the patient;         and wherein a risk of somnolence and dizziness for the patient         who has moderate renal impairment is lower following orally         administering the dosage form containing the combination once a         day to the patient than it would be if a combination of 105 mg         of bupropion hydrochloride and 45 mg of dextromethorphan         hydrobromide were administered twice a day to the patient for         the same number of days.

Some embodiments include a method of treating a patient with a combination of dextromethorphan and bupropion, wherein the patient is experiencing a nervous system condition, the method comprising the steps of:

-   -   determining whether the patient has moderate renal impairment         by:         -   obtaining or having obtained a biological sample from the             patient; and         -   performing or having performed an assay on the biological             sample to determine if the patient has moderate renal             impairment; and     -   if the patient has moderate renal impairment, then orally         administering once a day to the patient, a dosage form         containing a combination of 105 mg or less of bupropion         hydrochloride, or a molar equivalent amount of the free base or         another salt form of bupropion, and 45 mg or less of         dextromethorphan hydrobromide, or a molar equivalent amount of         the free base or another salt form of dextromethorphan, wherein         the molar ratio of the bupropion to the dextromethorphan is         about the ratio of the molar amount of bupropion in 105 mg of         bupropion hydrochloride to the molar amount of dextromethorphan         in 45 mg of dextromethorphan hydrobromide;     -   if the patient does not have renal impairment, then orally         administering twice a day to the patient, a dosage form         containing a combination of 105 mg of bupropion hydrochloride,         or a molar equivalent amount of the free base or another salt         form of bupropion, and 45 mg of dextromethorphan hydrobromide,         or a molar equivalent amount of the free base or another salt         form of dextromethorphan;     -   wherein a risk of somnolence and dizziness for a patient who has         moderate renal impairment is lower following orally         administering the dosage form containing the combination once a         day to the patient than it would be if a combination of 105 mg         of bupropion hydrochloride and 45 mg of dextromethorphan         hydrobromide were administered twice a day to the patient for         the same number of days.

Some embodiments include a method of treating major depressive disorder in a human patient who requires concomitant treatment with a strong CYP2D6 inhibitor, comprising administering, once daily to the human patient, a combination of about 105 mg of bupropion hydrochloride and about 45 mg of dextromethorphan hydrobromide, wherein the human patient is experiencing major depressive disorder and is receiving concomitant treatment with the strong CYP2D6 inhibitor. In some embodiments, the strong CYP2D6 inhibitor is paroxetine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the effects of renal impairment, hepatic impairment, and CYP2D6 poor metabolizer status on the pharmacokinetics of a tablet containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride.

DETAILED DESCRIPTION

As mentioned above, this disclosure relates to administration of a combination of: 1) about 100-110 mg, about 104-106 mg, or about 105 mg of bupropion hydrochloride, or a molar equivalent amount of a free base form or another salt form of dextromethorphan; and 2) about 40-50 mg, about 44-46 mg, or about 45 mg of dextromethorphan hydrobromide, or a molar equivalent amount of a free base form or another salt form of dextromethorphan. This combination is referred to for convenience herein as the “subject combination.” In every instance where the subject combination is referred to herein, the combination of 105 mg of bupropion hydrochloride and 45 mg of dextromethorphan hydrobromide is specifically contemplated.

Strong CYP2D6 inhibitors include, but are not limited to, compounds such as fluoxetine, propafenone, quinidine, and paroxetine.

Dextromethorphan hydrobromide is an uncompetitive NMDA receptor antagonist and sigma-1 receptor agonist.

The chemical name of dextromethorphan hydrobromide is morphinan, 3-methoxy-17-methyl-, (9a, 13a, 14a), hydrobromide monohydrate. Dextromethorphan hydrobromide has the empirical formula C₁₈H₂₅NO·HBr·H₂O and a molecular weight of 370.33. The structural formula is:

Dextromethorphan hydrobromide powder is white or almost white, crystalline, and sparingly soluble in water.

Bupropion hydrochloride is an aminoketone and CYP450 2D6 inhibitor.

The chemical name of bupropion hydrochloride is: (±)-1-(3-chlorophenyl)-2-[(1,1-dimethylethyl)amino]-1-propanone hydrochloride. Bupropion hydrochloride has the empirical formula C₁₃H₁₈CINO·HCl and a molecular weight of 276.2. The structural formula is:

Bupropion hydrochloride powder is white and highly soluble in water.

The subject combination may be contained in an oral dosage form, including a tablet, such as an extended-release tablet. In some embodiments, the subject combination is contained in a dosage form for oral administration and is available as round bilayer tablets.

In some embodiments, each tablet containing the subject combination contains 45 mg of dextromethorphan hydrobromide in an immediate-release formulation. In some embodiments, each tablet of the subject combination contains 105 mg of bupropion hydrochloride in an extended-release formulation. In some embodiments, each tablet of the subject combination contains 45 mg of dextromethorphan hydrobromide in an immediate-release formulation and 105 mg of bupropion hydrochloride in an extended-release formulation.

In some embodiments, a tablet containing the subject combination contains L-cysteine hydrochloride monohydrate. In some embodiments, a tablet containing the subject combination contains carbomer homopolymer. In some embodiments, a tablet containing the subject combination contains microcrystalline cellulose. In some embodiments, a tablet containing the subject combination contains colloidal silicon dioxide. In some embodiments, a tablet containing the subject combination contains crospovidone. In some embodiments, a tablet containing the subject combination contains stearic acid. In some embodiments, a tablet containing the subject combination contains magnesium stearate.

In some embodiments, a tablet containing the subject combination contains the following inactive ingredients: L-cysteine hydrochloride monohydrate, carbomer homopolymer, microcrystalline cellulose, colloidal silicon dioxide, crospovidone, stearic acid, and magnesium stearate.

In some embodiments, the starting dosage of the subject combination is 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride in one tablet that is administered once daily in the morning. In some embodiments, after 3 days, the dosage is increased to one tablet (or one dosage form containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride) twice daily, e.g., given at least 8 hours apart. In some embodiments, no more than two doses containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride are administered in the same day.

The subject combination may be administered orally with or without food. In some embodiments, the tablets are swallowed whole, and not crushed, divided, or chewed.

Patients having renal impairment may require special dosing. In some embodiments, the recommended dosage of the subject combination for patients with moderate renal impairment (estimated glomerular filtration rate (eGFR) or glomerular filtration rate (GFR) of 30 to 59 mL/minute/1.73 m2) is a daily dose of 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride, or a molar equivalent amount of another form of dextromethorphan and/or bupropion, such as administration of one tablet (or one dosage form containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride) once daily, such as one tablet or other oral dosage form daily in the morning, or twice daily oral administration of a combination of 52.5 mg of bupropion hydrochloride and about 22.5 mg of dextromethorphan hydrobromide. In some embodiments, the patients are monitored for adverse reactions potentially attributable to dextromethorphan, such as somnolence and dizziness.

Moderate renal impairment may be determined by an assay, such as an assay that determines creatine levels, on a biological sample from the patient, such as a blood sample. Creatine levels from a blood sample can be used to estimate GFR.

Patients who are concomitantly using the subject combination with strong CYP2D6 inhibitors may require special dosing. Concomitant use of the subject combination with a strong CYP2D6 inhibitor increases plasma concentrations of dextromethorphan. In some embodiments, the recommended dosage of the subject combination when coadministered with a strong CYP2D6 inhibitor is one tablet (or one dosage form containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride) once daily, such as one tablet or other oral dosage form daily in the morning. In some embodiments, the patients are monitored for adverse reactions potentially attributable to dextromethorphan, such as somnolence and dizziness.

Patients who are known CYP2D6 poor metabolizers (PMs) may require special dosing. In some embodiments, the recommended dosage for patients known to be poor CYP2D6 metabolizers is one tablet (or one dosage form containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride) once daily, such as one tablet or other oral dosage form daily in the morning.

Special precautions may be required when switching a patient to or from a monoamine oxidase inhibitor (MAOI) antidepressant to the subject combination. In some embodiments, at least 14 days must elapse between discontinuation of an MAOI intended to treat depression and initiation of therapy with the subject combination. Conversely, in some embodiments, at least 14 days must be allowed after stopping the subject combination before starting an MAOI antidepressant.

In the subject combination, bupropion inhibits the metabolism of dextromethorphan via CYP2D6. Dextromethorphan, when co-administered with bupropion, displays nonlinear pharmacokinetics at steady state, with greater than dose-proportional changes in AUC and C_(max) for varying doses of dextromethorphan (30 to 60 mg) and less than dose-proportional changes for varying doses of bupropion (75 to 150 mg).

Steady state plasma concentrations of dextromethorphan and bupropion when given as the subject combination are achieved within 8 days. The accumulation ratios for dextromethorphan at steady state are about 20 and about 32, respectively based on C_(max) and AUC_(0_12). The accumulation ratios for bupropion at steady state are 1.1 and 1.5, respectively based on C_(max) and AUC₀₋₁₂.

After administration of the subject combination, the median T_(max) of dextromethorphan is about 3 hours and the median T_(max) of bupropion is about 2 hours. The C_(max) of hydroxybupropion metabolite occurs approximately 3 hours post-dose and is approximately 14 times the peak level of bupropion. The AUC₀₋₂ hydroxybupropion is about 19 times that of bupropion. The C_(max) of the erythrohydroxybupropion and threohydroxybupropion metabolites occurs approximately 4 hours post-dose and is approximately equal to and about 5 times that of bupropion, respectively. The AUC₀₋₁₂ values of erythrohydroxybupropion and threohydroxybupropion are about 1.2 and about 7 times that of bupropion, respectively.

The subject combination can be taken with or without food. Dextromethorphan C_(max) and AUC₀₋₂ were unchanged and decreased by 14%, respectively, and bupropion C_(max) and AUC₀₋₂ were increased by 3% and 6%, respectively, when the subject combination was administered with food.

The plasma protein binding of dextromethorphan is approximately 60-70% and bupropion is 84%. The extent of protein binding of the hydroxybupropion metabolite is similar to that for bupropion; whereas the extent of protein binding of the threohydroxybupropion metabolite is about half that seen with bupropion.

Following 8 days of administration of the subject combination in extensive metabolizers, the mean elimination half-life of dextromethorphan was increased approximately 3-fold to about 22 hours, as compared to dextromethorphan given without bupropion.

The mean elimination half-life of dextromethorphan and bupropion was 22 hours and 15 hours, respectively. The apparent elimination half-life of hydroxybupropion, erythrohydroxybuporpion and threohydroxybupropion metabolites were approximately 35, 44 and 33 hours, respectively.

Esketamine is a non-competitive NMDA receptor antagonist indicated, in conjunction with an oral antidepressant, for the treatment of treatment-resistant depression in adults. Treatment of treatment-resistant depression carries a risk of dissociation. The label for esketamine states that because of the risks of sedation and dissociation, patients must be monitored for at least 2 hours at each treatment session, followed by an assessment to determine when the patient is considered clinically stable and ready to leave the healthcare setting.

Dissociation includes: delusional perception; depersonalization/derealization disorder; derealization; diplopia; dissociation; dysesthesia; feeling cold; feeling hot; feeling of body temperature change; hallucination; hallucination, auditory; hallucination, visual; hyperacusis; illusion; ocular discomfort; oral dysesthesia; paranesthesia; paranesthesia oral; pharyngeal paranesthesia; photophobia; time perception altered; tinnitus; vision blurred; visual impairment.

The subject combination is a combination of dextromethorphan, an uncompetitive N-methyl D-aspartate (NDMA) receptor antagonist and sigma-1 receptor agonist, and bupropion, an aminoketone and CYP450 2D6 inhibitor, indicated for the treatment of major depressive disorder (MDD) in adults. Unlike esketamine, the subject combination can be administered as a without dissociation or dissociative events. In some embodiments, the patient is not monitored for dissociation after the subject combination is administered.

Unlike the combination of quinidine and dextromethorphan, at a dose of a combination of 105 mg of bupropion hydrochloride and 45 mg of dextromethorphan hydrobromide given twice a day, the subject combination does not prolong the QT interval to any clinically relevant extent. Thus, for a human patient who is experiencing major depressive disorder and is at risk of QT prolongation and torsades de pointer, electrocardiographic evaluation of QT interval is not typically conducted on the human patient.

The subject combination may be used for adjunctive treatment of major depressive disorder or depression.

In addition to major depressive disorder, the subject combination may be used to treat other diseases in conditions in the patient populations or circumstances described herein. For example, the subject combination may be used to treat pain or a neurological disorder. Examples of neurological disorders that may be treated with the subject combination include, but are not limited to: affective disorders, psychiatric disorders, cerebral function disorders, movement disorders, dementias, motor neuron diseases, neurodegenerative diseases, seizure disorders, and headaches.

Affective disorders that may be treated by the subject combination include, but are not limited to, depression, major depression, treatment resistant depression, treatment resistant bipolar depression, bipolar disorders including cyclothymia, seasonal affective disorder, mood disorders, chronic depression (dysthymia), psychotic depression, postpartum depression, premenstrual dysphoric disorder (PMDD), situational depression, atypical depression, mania, anxiety disorders, attention deficit disorder (ADD), attention deficit disorder with hyperactivity (ADDH), and attention deficit/hyperactivity disorder (AD/HD), bipolar and manic conditions, obsessive-compulsive disorder, bulimia, obesity or weight-gain, narcolepsy, chronic fatigue syndrome, premenstrual syndrome, substance addiction or abuse, nicotine addiction, psycho-sexual dysfunction, pseudobulbar affect, and emotional lability.

Depression may be manifested by depressive symptoms. These symptoms may include psychological changes such as changes in mood, feelings of intense sadness, despair, mental slowing, loss of concentration, pessimistic worry, agitation, anxiety, irritability, guilt, anger, feelings of worthlessness, reckless behavior, suicidal thoughts, or attempts, and/or self-deprecation. Physical symptoms of depression may include insomnia, anorexia, appetite loss, weight loss, weight gain, decreased energy and libido, fatigue, restlessness, aches, pains, headaches, cramps, digestive issues, and/or abnormal hormonal circadian rhythms.

Psychiatric disorders that may be treated by the subject combination, include, but are not limited to, anxiety disorders, including but not limited to, phobias, generalized anxiety disorder, social anxiety disorder, panic disorder, agoraphobia, obsessive-compulsive disorder, and post-traumatic stress disorder (PTSD); mania, manic depressive illness, hypomania, unipolar depression, depression, stress disorders, somatoform disorders, personality disorders, psychosis, schizophrenia, delusional disorder, schizoaffective disorder, schizotypy, aggression, aggression in Alzheimer's disease, agitation, and agitation in Alzheimer's disease. Alzheimer's disease may also be referred to as dementia of the Alzheimer's type. Other neurobehavioral symptoms of Alzheimer's disease that may be treated include disinhibition and apathy.

Agitation in Alzheimer's disease occurs as the disease progresses. Agitation may present itself as inappropriate verbal, emotional, and/or physical behaviors. Inappropriate behaviors may include, but are not limited to, incoherent babbling, inappropriate emotional response, demands for attention, threats, irritability, frustration, screaming, repetitive questions, mood swings, cursing, abusive language, physical outbursts, emotional distress, restlessness, shredding, sleeping disturbances, delusions, hallucinations, pacing, wandering, searching, rummaging, repetitive body motions, hoarding, shadowing, hitting, scratching, biting, combativeness, hyperactivity, and/or kicking.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, and behavioral and psychological symptoms including agitation. AD is the most common form of dementia and afflicts an estimated 6 million individuals in the United States, a number that is anticipated to increase to approximately 14 million by 2050. Agitation is reported in up to 70% of patients with AD and is characterized by emotional distress, aggressive behaviors, disruptive irritability, and disinhibition. Managing agitation is a priority in AD. Agitation in patients with AD has been associated with increased caregiver burden, decreased functioning, accelerated cognitive decline, earlier nursing home placement, and increased mortality. There are currently no therapies approved by the FDA for the treatment of agitation in patients with AD.

Neurobehavioral symptoms have been known to appear during dementia and may be treated by the combination. Caregivers or families may feel more overwhelmed by patients' behavioral/psychological symptoms than by their cognitive impairment. Common forms of the syndrome are Alzheimer's disease, vascular dementia, dementia with Lewy bodies (abnormal aggregates of protein that develop inside nerve cells), and a group of diseases that contribute to frontotemporal dementia (degeneration of the frontal lobe of the brain). The symptoms that dementia patients have are similar to those of psychiatric disorders, but some are slightly different from each other. Neurobehavioral symptoms associated with dementia include depression, apathy, agitation, disinhibition, hallucinations, delusions, psychosis, impulsiveness, aggressiveness, compulsion, excessive sex drive, and personality disorders. Neurobehavioral symptoms such as disinhibition may also be found in other conditions such as traumatic brain injury.

Agitation in patients with Alzheimer's disease may be assessed using the Cohen Mansfield Agitation Inventory or CMAI. The CMAI assesses various behaviors including, Hitting (including self), Kicking, Grabbing onto people, Pushing, Throwing things, Biting, Scratching, Spitting, Hurting self or others, Tearing things or destroying property, Making physical sexual advances, Pacing, aimless wandering, Inappropriate dress or disrobing, Trying to get to a different place, Intentional falling, Eating/drinking inappropriate substances, Handling things inappropriately, Hiding things, Hoarding things, Performing repetitive mannerisms, General restlessness, Screaming, Making verbal sexual advances, Cursing or verbal aggression, Repetitive sentences or questions, Strange noises (weird laughter or crying), Complaining, Negativism, Constant unwarranted request for attention or help.

Schizophrenia may treated by the combination including positive symptoms and/or negative symptoms of schizophrenia, or residual symptoms of schizophrenia. Other conditions that may treated include intermittent explosive disorder.

Cerebral function disorders that may be treated by the subject combination include, but are not limited to, disorders involving intellectual deficits such as senile dementia, Alzheimer's type dementia, memory loss, amnesia/amnestic syndrome, epilepsy, disturbances of consciousness, coma, lowering of attention, speech disorders, voice spasms, Parkinson's disease, Lennox-Gastaut syndrome, autism, hyperkinetic syndrome, and schizophrenia. Cerebral function disorders also include disorders caused by cerebrovascular diseases including, but not limited to, stroke, cerebral infarction, cerebral bleeding, cerebral arteriosclerosis, cerebral venous thrombosis, head injuries, and the like where symptoms include disturbance of consciousness, senile dementia, coma, lowering of attention, and speech disorders.

Substance addiction abuse that may be treated by the subject combination includes, but is not limited to, drug dependence, addiction to cocaine, psychostimulants (e.g., crack, cocaine, speed, meth), nicotine, alcohol, opioids, anxiolytic and hypnotic drugs, cannabis (marijuana), amphetamines, hallucinogens, phencyclidine, volatile solvents, and volatile nitrites. Nicotine addiction includes nicotine addiction of all known forms, such as smoking cigarettes, cigars and/or pipes, e-cigarettes or vaping, and addiction to chewing tobacco.

Movement disorders that may be treated by the subject combination include, but are not limited to, akathisia, akinesia, associated movements, athetosis, ataxia, ballismus, hemiballismus, bradykinesia, cerebral palsy, chorea, Huntington's disease, Huntington's disease chorea, rheumatic chorea, Sydenham's chorea, dyskinesia, tardive dyskinesia, dystonia, blepharospasm, spasmodic torticollis, dopamine-responsive dystonia, Parkinson's disease, restless legs syndrome (RLS), tremor, essential tremor, and Tourette's syndrome, and Wilson's disease.

Dementias that may be treated by the subject combination include, but are not limited to, Alzheimer's disease, Parkinson's disease, vascular dementia, dementia with Lewy bodies, mixed dementia, fronto-temporal dementia, Creutzfeldt-Jakob disease, normal pressure hydrocephalus, Huntington's disease, Wernicke-Korsakoff Syndrome, and Pick's disease.

Motor neuron diseases that may be treated by the subject combination include, but are not limited to, amyotrophic lateral sclerosis (ALS), progressive bulbar palsy, primary lateral sclerosis (PLS), progressive muscular atrophy, post-polio syndrome (PPS), spinal muscular atrophy (SMA), spinal motor atrophies, Tay-Sach's disease, Sandhoff disease, and hereditary spastic paraplegia.

Neurodegenerative diseases that may be treated the subject combination include, but are not limited to, Alzheimer's disease, prion-related diseases, cerebellar ataxia, spinocerebellar ataxia (SCA), spinal muscular atrophy (SMA), bulbar muscular atrophy, Friedrich's ataxia, Huntington's disease, Lewy body disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease), multiple sclerosis (MS), multiple system atrophy, Shy-Drager syndrome, corticobasal degeneration, progressive supranuclear palsy, Wilson's disease, Menkes disease, adrenoleukodystrophy, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), muscular dystrophies, Charcot-Marie-Tooth disease (CMT), familial spastic paraparesis, neurofibromatosis, olivopontine cerebellar atrophy or degeneration, striatonigral degeneration, Guillain-Barré syndrome, and spastic paraplesia.

Seizure disorders that may be treated by the subject combination include, but are not limited to, epileptic seizures, nonepileptic seizures, epilepsy, febrile seizures; partial seizures including, but not limited to, simple partial seizures, Jacksonian seizures, complex partial seizures, and epilepsia partialis continua; generalized seizures including, but not limited to, generalized tonic-clonic seizures, absence seizures, atonic seizures, myoclonic seizures, juvenile myoclonic seizures, and infantile spasms; and status epilepticus.

Types of headaches that may be treated by the subject combination include, but are not limited to, migraine, tension, and cluster headaches.

Other neurological disorders that may be treated by the subject combination include, Rett Syndrome, autism, tinnitus, disturbances of consciousness disorders, sexual dysfunction, intractable coughing, narcolepsy, cataplexy; voice disorders due to uncontrolled laryngeal muscle spasms, including, but not limited to, abductor spasmodic dysphonia, adductor spasmodic dysphonia, muscular tension dysphonia, and vocal tremor; diabetic neuropathy, chemotherapy-induced neurotoxicity, such as methotrexate neurotoxicity; incontinence including, but not limited, stress urinary incontinence, urge urinary incontinence, and fecal incontinence; and erectile dysfunction.

In some embodiments, the subject combination may be used to treat pain, joint pain, pain associated with sickle cell disease, pseudobulbar affect, depression (including treatment resistant depression), disorders related to memory and cognition, schizophrenia, Parkinson's disease, amyotrophic lateral sclerosis (ALS), Rhett's syndrome, seizures, cough (including chronic cough), etc.

In some embodiments, the subject combination may be administered orally to relieve musculoskeletal pain including low back pain, and pain associated with rheumatoid arthritis, juvenile rheumatoid arthritis, osteoarthritis, erosive osteoarthritis, sero-negative (non-rheumatoid) arthropathies, non-articular rheumatism, peri-articular disorders, axial spondyloarthritis including ankylosing spondylitis, Paget's disease, fibrous dysplasia, SAPHO syndrome, transient osteoarthritis of the hip, vertebral crush fractures, osteoporosis, etc.

In some embodiments, the subject combination may be administered to relieve inflammatory pain including musculoskeletal pain, arthritis pain, and complex regional pain syndrome.

Arthritis refers to inflammatory joint diseases that can be associated with pain. Examples of arthritis pain include pain associated with osteoarthritis, erosive osteoarthritis, rheumatoid arthritis, juvenile rheumatoid arthritis, sero-negative (non-rheumatoid) arthropathies, non-articular rheumatism, peri-articular disorders, neuropathic arthropathies including Charcot's foot, axial spondyloarthritis including ankylosing spondylitis, and SAPHO syndrome.

In some embodiments, the subject combination is used to treat chronic musculoskeletal pain.

In some embodiments, the subject composition may be administered to relieve complex regional pain syndrome, such as complex regional pain syndrome type I (CRPS-I), complex regional pain syndrome type II (CRPS-II), CRPS-NOS, or another type of CRPS. CRPS is a type of inflammatory pain. CRPS can also have a neuropathic component. Complex regional pain syndrome is a debilitating pain syndrome. It is characterized by severe pain in a limb that can be accompanied by edema, and autonomic, motor, and sensory changes.

In some embodiments, the subject composition may be administered orally to relieve neuropathic pain.

Examples of neuropathic pain include pain due to diabetic peripheral neuropathy or diabetic peripheral neuropathic pain, post-herpetic neuralgia, trigeminal neuralgia, monoradiculopathies, phantom limb pain, central pain, pain due to multiple sclerosis, etc. Other causes of neuropathic pain include cancer-related pain, lumbar nerve root compression, spinal cord injury, post-stroke pain, central multiple sclerosis pain, HIV-associated neuropathy, and radio- or chemo-therapy associated neuropathy, etc.

In some embodiments, the subject composition may be administered to relieve fibromyalgia.

In some embodiments, the subject composition may be co-administered with one or more strong Inhibitors of CYP2D6. It has been found that the concomitant use of the subject combination with one or more strong CYP2D6 inhibitors increases plasma concentrations of dextromethorphan. It is thus recommended to monitor patients for adverse effects or adverse reactions potentially attributable to dextromethorphan, such as somnolence and dizziness.

The dosage adjustment may be necessary when the subject composition is co-administered with one or more strong inhibitors of CYP2D6. Adjusting to a lower dose amount of the bupropion and/or the dextromethorphan in the subject combination or less frequent dosing of the subject combination may reduce adverse effects or adverse reactions, such as, but not limited to, somnolence, dizziness, or a combination thereof in a patient. For example, a recommended dosage of the subject combination when co-administered with one or more strong CYP2D6 inhibitors, is one tablet containing 45 mg or less of dextromethorphan hydrobromide and 105 mg or less of bupropion hydrochloride once daily, such as once daily in the morning.

Administration of the subject combination once a day to patients who are receiving a concomitant strong CYP2D6 may reduce the adverse effects, such as, but not limited to, somnolence, dizziness, or a combination thereof, as compared to administration of the subject combination twice a day for same number of days. In some embodiments, reducing the dose amount or dose frequency of the subject combination may reduce somnolence. In some embodiments, reducing dose amount or dose frequency may reduce dizziness. As dizziness may link to falls, adjusting the dosage to lower amount or lower dose frequency of the subject combination may reduce the risk of falls for a patient taking the subject combination. For example, taking the subject combination once a day may reduce the risk of falls for a patient as compared to taking the subject combination twice a day for same number of days. This may be important, for example, to elderly patients or patients suffering from a dementia, such as Alzheimer's disease.

In some embodiments, the subject composition may be administered to a patient who has moderate renal impairment. As explained herein, it has been found that administering the subject composition to CYP2D6 poor metabolizers increases plasma concentrations of dextromethorphan as compared to patients who are not CYP2D6 poor metabolizers. It is thus recommended to monitor patients for adverse effects or adverse reactions potentially attributable to dextromethorphan, such as somnolence and dizziness.

Dosage adjustment may be necessary when the patient has moderate renal impairment. Adjusting to a lower dose amount of the bupropion and/or the dextromethorphan in the subject combination or less frequent dosing of the subject combination may reduce adverse effects or adverse reactions, or a risk of adverse effects or adverse reactions, such as, but not limited to, somnolence, dizziness, or a combination thereof in a patient. For example, a recommended dosage of the subject combination when administered to a patient who has moderate renal impairment, is one tablet containing 45 mg or less of dextromethorphan hydrobromide and 105 mg or less of bupropion hydrochloride once daily, such as once daily in the morning.

Administration of the subject combination once a day to patients who have moderate renal impairment may reduce the adverse effects, or the risk of adverse effects, such as, but not limited to, somnolence, dizziness, or a combination thereof, as compared to administration of the subject combination twice a day for same number of days. In some embodiments, reducing the dose amount or dose frequency of the subject combination may reduce somnolence. In some embodiments, reducing dose amount or dose frequency may reduce dizziness. As dizziness may link to falls, adjusting the dosage to lower amount or lower dose frequency of the subject combination may reduce the risk of falls for a patient taking the subject combination. For example, taking the subject combination once a day may reduce the risk of falls for a patient as compared to taking the subject combination twice a day for same number of days. This may be important, for example, to elderly patients or patients suffering from a dementia, such as Alzheimer's disease.

The term “treating” or “treatment” includes the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals, or any activity that otherwise affects the structure or any function of the body of man or other animals.

A subject combination may be used to treat any disease or condition identified as treatable by the combination of bupropion and dextromethorphan in any of the following U.S. Pat. Nos. 8,569,328, 9,168,234, 9,189,905 9,205,083, 9,238,032, 9,278,095, 9,314,462, 9,370,513, 9,375,429, 9,408,815, 9,421,176, 9,457,023, 9,457,025, 9,474,731, 9,486,450, 9,700,528, 9,700,553, 9,707,191, 9,763,932, 9,861,595, 9,867,819, 9,968,568, 10,058,518, 10,064,857, 10,080,727, 10,092,560, 10,092,561, 10,105,327, 10,105,361, 10,251,879, 10,463,634, 10,512,643, 10,548,857, 10,596,167, 10,772,850, 10,780,064, 10,780,066, 10,786,469, 10,786,496, 10,799,497, 10,806,710, 10,864,209, 10,874,663, 10,874,664, 10,874,665, 10,881,624, 10,881,657, 10,894,046, 10,894,047, 10,898,453, all of which are incorporated by reference herein in their entireties for their disclosure of diseases that may be treated by a combination of bupropion and dextromethorphan, including specific embodiments and combinations described therein.

The following U.S. Provisional applications are also incorporated by reference herein in their entireties: Ser. No. 63/359,143, filed Jul. 7, 2022, Ser. No. 63/370,592, filed Aug. 5, 2022, Ser. No. 63/396,182, filed Aug. 8, 2022, Ser. No. 63/373,040, filed Aug. 19, 2022, and Ser. No. 63/401,541, filed Aug. 26, 2022.

Example 1

In a study of the subject combination in 7 subjects with moderate (GFR 30-60 mL/min) renal impairment compared to 6 matched controls with normal renal function (matched in gender, age, and weight range to impaired subjects), both dextromethorphan and bupropion exposures increased by approximately 2-fold and clearances were reduced by 50%.

Example 2

Approximately 7 to 10% of Caucasians and 3 to 8% of African Americans lack the capacity to metabolize CYP2D6 substrates and are classified as poor metabolizers. In 3 poor metabolizers the pharmacokinetics of the subject combination resulted in an approximate 3-fold and 3.4-fold increase in dextromethorphan C_(max) and AUC₀₋₁₂, respectively, compared to extensive metabolizers. An exploration of steady state pharmacokinetic data in 12 poor metabolizers treated with the subject combination in efficacy trials showed plasma concentrations of dextromethorphan that were generally higher than exposures for non-poor metabolizers.

Example 3

Co-administration of the SSRI paroxetine and the subject combination was studied in 29 healthy volunteers. Paroxetine increased the overall exposure of dextromethorphan by 2.5-fold and had no effect on bupropion. The overall exposure of paroxetine was increased by 1.2-fold when co-administered with the subject combination. Based on these results, when the subject combination is prescribed with drugs that inhibit CYP2D6, the subject combination should be dosed once daily. Use caution when administering the subject combination in conjunction with drugs which are extensively metabolized via CYP2D6.

Example 4

The properties of a tablet containing a combination of dextromethorphan hydrobromide, which is an uncompetitive NMDA receptor antagonist and sigma-1 receptor agonist, and bupropion hydrochloride, which is an aminoketone and CYP450 2D6 inhibitor, were studied.

The tablets are for oral administration and are round bilayer tablets. Each tablet contains 45 mg dextromethorphan hydrobromide (equivalent to 32.98 mg of the dextromethorphan free base) in an immediate-release formulation and 105 mg bupropion hydrochloride (equivalent to 91.14 mg of the bupropion free base) in an extended-release formulation. Each tablet contains the following inactive ingredients: carbomer homopolymer, colloidal silicon dioxide, crospovidone, glyceryl monocaprylocaprate, L-cysteine hydrochloride monohydrate, magnesium stearate, microcrystalline cellulose, polyvinyl alcohol, red iron oxide, sodium lauryl sulfate, stearic acid, talc, titanium dioxide, and/or yellow iron oxide.

The effects of renal impairment, hepatic impairment, and CYP2D6 poor metabolizer status on the exposure to a tablet containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride are summarized in Table 1 and FIG. 1 .

TABLE 1 PK Change relative to Patients Group Parameter reference (90% CI) Moderate Renal Impairment 1 DM AUC 2.21 (1.24, 3.97) Moderate Renal Impairment 1 DM C_(max) 2.10 (1.17, 3.77) Moderate Renal Impairment 1 BUP AUC 1.80 (1.12, 2.92) Moderate Renal Impairment 1 BUP C_(max) 1.87 (1.07, 3.27) Moderate Hepatic Impairment 2 DM AUC 1.17 (0.85, 1.61) Moderate Hepatic Impairment 2 DM C_(max) 1.21 (0.90, 1.62) Moderate Hepatic Impairment 2 BUP AUC 1.36 (0.86, 2.15) Moderate Hepatic Impairment 2 BUP C_(max) 1.44 (0.90, 2.30) CYP2D6 Poor Metabolizer 3 DM AUC 3.40 (2.08, 5.57) CYP2D6 Poor Metabolizer 3 DM C_(max) 3.00 (1.98, 4.54) CYP2D6 Poor Metabolizer 3 BUP AUC 1.04 (0.77, 1.41) CYP2D6 Poor Metabolizer 3 BUP C_(max) 0.97 (0.67, 1.41)

Results depicted in FIG. 1 are based on plasma concentrations in human patients after 8 days of twice daily dosing of a tablet containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride. Data are GMRs and 90% CIs. Reference used are the matched healthy subjects for renal and hepatic impairment studies, and extensive or ultra-extensive CYP2D6 metabolizers. AUC represents the area under the plasma concentration-time curve from zero to 12 hours; BUP represents bupropion; CI is confidence interval; C_(max) is maximum plasma concentration; DM represents dextromethorphan; GMRs represents geometric mean ratios; PK represents pharmacokinetics.

For patients having moderate renal impairment, a 2.21-fold increase in dextromethorphan AUC₀₋₂, a 2.10-fold increase in dextromethorphan C_(max), a 1.80-fold increase in bupropion AUC₀₋₂, and a 1.87-fold increase in bupropion C_(max) were observed.

Based upon these results, dosage adjustment is recommended in patients known to have moderate renal impairment because these patients have higher dextromethorphan and bupropion concentrations than patients with healthy renal function. The recommended total daily dose for patients known to have moderate renal impairment is about 45 mg of dextromethorphan hydrobromide and about 105 mg of bupropion hydrochloride (e.g. one tablet containing about 45 mg of dextromethorphan hydrobromide and about 105 mg of bupropion hydrochloride for administration once daily, such as in the morning), or an equivalent dose of another form dextromethorphan and/or bupropion.

Example 5

The properties of a tablet containing a combination of dextromethorphan hydrobromide, which is an uncompetitive NMDA receptor antagonist and sigma-1 receptor agonist, and bupropion hydrochloride, which is an aminoketone and CYP450 2D6 inhibitor, were studied.

The tablets are for oral administration and are round bilayer tablets. Each tablet contains 45 mg dextromethorphan hydrobromide (equivalent to 32.98 mg of the dextromethorphan free base) in an immediate-release formulation and 105 mg bupropion hydrochloride (equivalent to 91.14 mg of the bupropion free base) in an extended-release formulation. Each tablet contains the following inactive ingredients: carbomer homopolymer, colloidal silicon dioxide, crospovidone, glyceryl monocaprylocaprate, L-cysteine hydrochloride monohydrate, magnesium stearate, microcrystalline cellulose, polyvinyl alcohol, red iron oxide, sodium lauryl sulfate, stearic acid, talc, titanium dioxide, and/or yellow iron oxide.

The effect of concomitantly administered 20 mg of paroxetine on the dextromethorphan exposure to patients taking, twice daily, a tablet containing 45 mg of dextromethorphan hydrobromide and 105 mg of bupropion hydrochloride was determined. Dextromethorphan AUC₀₋₂ was increased 2.69-fold and dextromethorphan C_(max) was increased 2.38-fold as compared to patients taking the tablet twice daily without paroxetine.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as amounts, percentage, and so forth used in the specification and claims are to be understood in all instances as indicating both the exact values as shown and as being modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Use of the term “comprising” or “comprises” herein also contemplates that use of “consisting essentially of,” “consists essentially of,” “consisting of,” or “consists of” in its place.

Affirmative recitation of an element anywhere herein should be understood to contemplate both including and excluding that element.

The terms “a,” “an,” “the” and similar referents used in the context of describing the embodiments (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of any claim. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the claims.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from a group, for reasons of convenience and/or to expedite prosecution. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups if used in the appended claims.

Certain embodiments are described herein, including the best mode known to the inventors for carrying out the claimed embodiments. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the claimed embodiments to be practiced otherwise than specifically described herein. Accordingly, the claims include all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context.

In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the claims. Other modifications that may be employed are within the scope of the claims. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the claims are not limited to embodiments precisely as shown and described. 

The invention claimed is:
 1. A method of treating major depressive disorder in a human patient who requires concomitant treatment with paroxetine, comprising administering, once daily to the human patient, a combination of about 105 mg of bupropion hydrochloride and about 45 mg of dextromethorphan hydrobromide, wherein the human patient is experiencing major depressive disorder and is receiving concomitant treatment with paroxetine, wherein the combination is present in a solid dosage form, wherein the solid dosage form is orally administered in the morning, wherein the dextromethorphan is in an immediate-release formulation, wherein the bupropion is in an extended-release formulation, and wherein the solid dosage form further contains L-cysteine hydrochloride monohydrate.
 2. The method of claim 1, wherein the once-daily administration avoids the human patient having an about 2.7-fold increase in AUC₀₋₁₂ of dextromethorphan as compared to the AUC₀₋₁₂ of dextromethorphan that would result after 8 days of twice daily administration of the solid dosage form to the human patient without the concomitant treatment with paroxetine.
 3. The method of claim 1, wherein the once-daily administration avoids the human patient having an about 2.4-fold increase in C_(max) of dextromethorphan as compared to the C_(max) of dextromethorphan that would result after 8 days of twice daily administration of the solid dosage form to the human patient without the concomitant treatment with paroxetine.
 4. The method of claim 1, wherein the solid dosage form further contains a carbomer homopolymer.
 5. The method of claim 1, wherein the solid dosage form further contains colloidal silicon dioxide.
 6. The method of claim 1, wherein the solid dosage form further contains crospovidone.
 7. The method of claim 1, wherein the solid dosage form further contains glyceryl monocaprylocaprate.
 8. The method of claim 1, wherein the solid dosage form further contains magnesium stearate.
 9. The method of claim 1, wherein the solid dosage form further contains microcrystalline cellulose.
 10. The method of claim 1, wherein the solid dosage form further contains polyvinyl alcohol.
 11. The method of claim 1, wherein the solid dosage form further contains red iron oxide.
 12. The method of claim 1, wherein the solid dosage form further contains sodium lauryl sulfate.
 13. The method of claim 1, wherein the solid dosage form further contains stearic acid.
 14. The method of claim 1, wherein the solid dosage form further contains talc.
 15. The method of claim 1, wherein the solid dosage form further contains titanium dioxide.
 16. The method of claim 1, wherein the solid dosage form further contains yellow iron oxide.
 17. The method of claim 1, wherein administration of the solid dosage form twice daily to the human patient for 8 days would result in the human patient having about the same AUC₀₋₁₂ of bupropion as compared to the AUC₀₋₁₂ of bupropion that would result after 8 days of twice daily administration of the solid dosage form to a human patient without the concomitant treatment with paroxetine.
 18. The method of claim 1, wherein administration of the solid dosage form twice daily to the human patient for 8 days would result in the human patient having about the same C_(max) of bupropion as compared to the C_(max) of bupropion that would result after 8 days of twice daily administration of the solid dosage form to a human patient without the concomitant treatment with paroxetine. 